The invention relates to an arrangement for a gas generator of a motor vehicle occupant protection system which has a filter chamber connected to the propellant chamber and equipped with filters for the gas flow.
Gas generators for air cushions are known in multiple constructions in automotive engineering. U.S. Pat. No. 4,561,675 shows a gas generator housing in which the propellant chamber, by way of openings, is connected with the filter chamber surrounding it. In the case of an ignition of the propellant, the gas flow is forcibly led through the filters arranged in the filter chamber. There is no compensation of the burn-off characteristics of the propellant which are a function of the ambient temperature.
A gas generator has become known from the EP-0069 441 (corresponding to U.S. Pat. No. 4,380,346) in which the gas outlet openings of the propellant chamber are closed off by means of tear foils which open up the path of the gas flow through the filters to the air cushion only when a minimum pressure is reached. Particularly at low ambient temperatures, this results in a considerable delay of the inflating of the air cushion.
It is an object of the invention to develop a gas generator having a filter chamber in such a manner that the dependence on temperature of the gas production exercises a considerably reduced influence on an inflating of the air cushion which takes place in time and is operationally reliable.
According to the invention, this object is achieved by providing an arrangement at an airbag gas generator for the temperature-dependent change-over of the paths of the gas flow generated by a propellant in the area of the filter chamber.
In certain preferred embodiments, the propellant gas flow pressure acts on one or more valve members to control the gas flow through the filter chamber as a function of propellant gas pressure, which propellant gas pressure is dependent on ambient temperatures.
In certain preferred embodiments, a valve member is provided which melts at a certain predetermined temperature of the propellant gas flow thereby opening in response to the temperature of the propellant gas flow.
In certain preferred embodiments, the selective propellant gas flow is provided by an arrangement with a filter chamber connected to a propellant chamber by way of openings and equipped with filters for the gas flow, comprising:
a partition provided in the filter chamber which has at least one first opening and at least one second opening, the at least one second opening is covered by means of the filters which form a main path for the gas flow,
and movable cover means for covering the at least one first opening, the characteristics of the material and dimensions of which movable cover means being selected to automatically close the at least one first opening above an adjustable threshold of the ambient temperature.
In certain preferred embodiments, the cover means is a cover member constructed of aluminum of preselected thickness.
Principal advantages of the invention include, on the one hand, that particularly in the case of low ambient temperatures, a higher operational reliability is achieved and, on the other hand, the amount of propellant may also be reduced. As a result, a lower peak pressure is reached at high ambient temperatures, whereby the operational reliability is increased because of the lower pressure load exercised on the housing and on the air cushion.
At the same time, because of the lower amount of propellant, the inherent weight of the gas generator is reduced and the amount of harmful substances generated during the burn-up is decreased.
Reference is made to related commonly assigned applications Ser. No. 07/541,954 filed June 22, 1990 (based on German Utility Model Application G 89 09 626.6, filed in Germany on Aug. 11, 1989) and Ser. No. 07/542,002, filed June 22, 1990 (based on German Patent Application P 39 24 500.4-21, filed in Germany on July 25, 1989).
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings